Two of the major functions of the human esophagus are the transport of food from intake to the stomach and the prevention of retrograde flow of gastrointestinal contents. The retrograde flow is, in part, prevented by two esophageal sphincters which normally remain closed and which are functional rather than distinct entities. In particular, a lower esophageal sphincter normally remains closed until parasympathetic activation causes its relaxation, allowing food to pass into the stomach from the esophagus. Various types of food and other activity may cause relaxation of the sphincter, such as fatty meals, smoking and beverages having xanthene content. Certain drugs or pharmaceuticals also may cause relaxation of this lower esophageal sphincter, as well as localized trauma or other problems such as neuromuscular disorders.
Regardless, patients having such difficulties may present with clinical indications including dysphagia, or difficulty in swallowing, as well as more classic symptoms of heartburn and other similar complaints. Recurrent problems of this nature often lead to a disorder known as reflux esophagitis, consisting of esophageal mucosa damage due to the interaction of the gastric or intestinal contents with portions of the esophagus having tissue not designed to experience such interaction. As suggested above, the causative agent for such problems may vary. Esophagitis can lead to a pre-cancerous condition, known as Barrett's Esophagus, which occurs when cells of the mucosal lining become damaged and are at risk of neoplasia.
As described for example in copending, commonly owned U.S. application Ser. No. 10/754,445, filed Jan. 9, 2004, a treatment catheter having an expandable electrode support can be used for treating a circumferential region of the esophagus in order to ablate an abnormal mucosal layer of the esophagus using radiofrequency (RF) energy. When successful, the treatment results in regeneration of a normal mucosal layer substantially free from metaplastic and other damage epithelial cells characteristic of Barrett's Esophagus.
In some instances, however, such radiofrequency ablation treatment may not be entirely successful and one or more regions of abnormal mucosa may remain. Alternatively, some patients initially present to the physician with small discrete regions of abnormal mucosa that are better suited to for selective ablation rather than circumferential ablation.